BLOWER

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2024-220157, filed on Dec. 16, 2024, the entire contents of which are incorporated herein by reference.

BACKGROUND

(i) Technical Field

The present disclosure relates to a blower.

(ii) Related Art

A blower with reduced noise is known (for example, see Japanese Unexamined Patent Application Publication No. H07-91392).

Some blowers include a fan case that accommodates a closed impeller that is a turbofan. In such blowers, it is also desired to suppress noise.

SUMMARY

According to an aspect of the present disclosure, there is provided a blower including: a motor; a closed impeller that is rotated by the motor and is a turbofan; and a fan case that accommodates the closed impeller, wherein the fan case includes a scroll portion surrounding the closed impeller, and a duct portion extending from the scroll portion, the scroll portion includes a suction port through which a rotation axis of the motor passes and through which gas is sucked, the duct portion includes a discharge port that discharges gas, and an inner peripheral edge of the suction port includes an arc edge extending in an arc shape about the rotation axis, and a straight edge extending in a straight line shape continuously from the arc edge when viewed in a direction of the rotation axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of a blower of a comparative example;

FIGS. 2A and 2B are explanatory views of a blower of the comparative example:

FIG. 3 is an explanatory view of a blower of the comparative example;

FIG. 4 is an external perspective view of a closed impeller;

FIG. 5A is a cross sectional view taken along line B-B in FIG. 2B, and FIG. 5B is a cross sectional view taken along line C-C in FIG. 2B;

FIG. 6A is an explanatory view of a suction port of a blower of the comparative example, and FIG. 6B is an explanatory view of an air flow in an upper case of the blower of the comparative example;

FIG. 7A is an explanatory view of a suction port of the blower of a first embodiment, and FIG. 7B is an explanatory view of an air flow in an upper case of the blower of the first embodiment;

FIGS. 8A and 8B are views illustrating blowers of the first embodiment in which angular positions of the suction port are different;

FIG. 9A is an explanatory view of a suction port of a blower of a second embodiment, and FIG. 9B is an explanatory view of an air flow in an upper case of the blower of the second embodiment;

FIGS. 10A and 10B are views illustrating blower of a second embodiment in which angular positions of the suction port are different;

FIG. 11A is an explanatory view of a suction port of a blower of a third embodiment, and FIG. 11B is an explanatory view of an air flow in an upper case of the blower of the third embodiment; and

FIGS. 12A and 12B are views illustrating blowers of a third embodiment in which angular positions of the suction port are different.

DETAILED DESCRIPTION

Comparative Example

Before describing a blower of the present embodiment, a blower 1x of a comparative example will be described. FIGS. 1, 2A, 2B, and 3 are explanatory views of the blower 1x of a comparative example. FIG. 1 is a perspective view of the blower 1x of the comparative example. FIG. 2A is a top view of the blower 1x of a comparative example. FIG. 2B of a side view of the blower 1x of the comparative example. FIG. 3 is a cross sectional view taken along line A-A in FIG. 2A.

The blower 1x includes a motor 10, a closed impeller 30, a bearing holding member 40, a motor case 50, a cable holder 55, and a fan case 70. FIG. 1 and other figures illustrate a rotation axis A of the motor 10 and a duct axis B of a duct portion 75 described later. The motor 10 is housed in the motor case 50. The closed impeller 30 is housed in the fan case 70. The closed impeller 30 is a turbofan. The cable holder 55 is attached to the motor case 50 and holds the plurality of cables C.

The fan case 70 includes an upper case 71 and a lower case 72 that are combined with each other. The fan case 70 includes a scroll portion 73 and the duct portion 75. A suction port 74 for taking gas into the fan case 70 is formed at the center above the scroll portion 73, in other words, at the center of the upper case 71. The rotation axis A passes through the suction port 74.

The duct portion 75 extends from the scroll portion 73 along the duct axis B. The duct axis B does not intersect the rotation axis A. The direction in which the duct axis B extends is perpendicular to the direction in which the rotation axis A extends. The duct axis B extends in a tangential direction of a circle centered on the rotation axis A and in a plane perpendicular to the rotation axis A. A discharge port 76 is formed at the tip of the duct portion 75. The scroll portion 73 has a constant width scroll flow passage P extending substantially annularly around the rotation axis A, which will be described in detail later. The gas introduced into the constant width scroll flow path P via the suction port 74 is discharged from the discharge port 76 of the duct portion 75. The area S4 of the suction port 74 illustrated in FIG. 2A is larger than the area S6 of the discharge port 76 illustrated in FIG. 2B.

The bearing holding member 40 includes a cylindrical portion 41 and a flange portion 42. The cylindrical portion 41 and the flange portion 42 face the lower surface side of the closed impeller 30. The cylindrical portion 41 has a substantially cylindrical shape. Two bearings 48 are held inside the cylindrical portion 41 to rotatably support a rotary shaft 13. The two bearings 48 support a substantially central portion of the rotary shaft 13. The flange portion 42 is fixed to an upper end portion of the cylindrical portion 41. A collar 44 is fixed to the outer peripheral portion of the cylindrical portion 41. A vibration proof member 45 is disposed between the collar 44 and the lower case 72. A nut 46 is screwed to the outer peripheral surface of the cylindrical portion 41. The collar 44 and the vibration proof member 45 are held between the nut 46 and the flange portion 42. The vibration proof member 45 separates the space in which the closed impeller 30 is housed and the space in which the motor 10 is housed.

The motor 10 includes a rotor 11, coils 16, insulators 17, a stator 18, and a printed circuit board 19. The rotor 11 includes the rotary shaft 13, a yoke 14, and a magnet 15. The rotation axis A of the motor 10 passes through the center of the rotary shaft 13 and is parallel to the rotary shaft 13. The closed impeller 30 is fixed to the tip of the rotary shaft 13. The yoke 14 is fixed to the proximal end of the rotary shaft 13. The magnet 15 is held on the outer periphery of the yoke 14. The magnet 15 has a cylindrical shape and is magnetized to different polarities in the circumferential direction. The rotary shaft 13, the yoke 14, and the magnet 15 rotate integrally.

The stator 18 is disposed radially outside the magnet 15. Each of the plurality of coils 16 is wound around the stator 18 via the insulator 17. The plurality of coils 16 are electrically connected to the printed circuit board 19. The plurality of cables C are connected to the printed circuit board 19. An electronic circuit provided outside the motor 10 and the printed circuit board 19 are electrically connected to each other via the plurality of cables C, so that energization of the plurality of coils 16 is controlled. When the plurality of coils 16 are energized, a magnetic force is generated between the stator 18 and the magnet 15. As a result, the closed impeller 30 rotates together with the rotor 11.

FIG. 4 is an external perspective view of the closed impeller 30. The closed impeller 30 includes a hub 31, blades 33, and a shroud 35. The hub 31 is formed in a substantially disc shape. The blades 33 are provided on the hub 31 at regular intervals in the circumferential direction. The shroud 35 is formed in a substantially disc shape. The shroud 35 is fixed to upper portions of the plurality of blades 33 and faces the hub 31 with a predetermined gap therebetween. An opening 352 is formed in the center of the shroud 35. The gas introduced into the fan case 70 through the suction port 74 passes through the gap between the blades 33 between the hub 31 and the shroud 35 through the opening 352, flows radially outward, and flows in the constant width scroll flow path P. A shaft hole 312 is formed in the center of the hub 31.

An outer circumferential edge 311 of the hub 31 is located radially outward of an outer circumferential edge 351 of the shroud 35. That is, the diameter of the hub 31 is larger than the diameter of the shroud 35, but the present disclosure is not limited thereto. For example, the diameter of the hub 31 and the diameter of the shroud 35 may be substantially the same.

Next, the constant width scroll flow passage P will be described with reference to FIGS. 3, 5A, and 5B. FIG. 5A is a cross sectional view taken along line B-B in FIG. 2B. FIG. 5B is a cross sectional view taken along line C-C in FIG. 2B. As illustrated in FIG. 3, the constant width scroll flow passage P is defined by an inner surface 711 of the upper case 71 and an inner surface 721 of the lower case 72. An upper portion of the inner surface 711 is curved in the cross sectional view of FIG. 3 and extends in a substantially annular shape around the rotation axis A. A lower portion of the inner surface 721 is curved in the cross sectional view of FIG. 3 and extends in a substantially annular shape around the rotation axis A. The inner surface 711 and the inner surface 721 face each other in a direction parallel to the rotation axis A.

As illustrated in FIGS. 3 and 5A, the inner surface 711 has an outer circumferential surface 712. The inner surface 721 has an outer circumferential surface 722 and an inner circumferential surface 723 that are opposite to each other in the radial direction. As illustrated in FIG. 5A, the radial distance between the outer circumferential surface 722 and the inner circumferential surface 723 is constant in the circumferential direction. That is, a width W1 of the constant width scroll passage P is constant in the circumferential direction about the rotation axis A.

As illustrated in FIG. 5B, the radial distance between the outer circumferential edge 311 of the hub 31 of the closed impeller 30 and the outer circumferential surface 712 of the upper case 71 is constant in the circumferential direction. Therefore, a width W2 between the outer circumferential edge 311 of the hub 31 and the outer circumferential surface 712 of the upper case 71 is constant in the circumferential direction. In addition, unlike the constant width scroll flow path P in the present embodiment, a widening scroll flow path whose width gradually increases in the circumferential direction toward the discharge port is known. The widening scroll flow passage has a higher fan efficiency than the constant width scroll flow passage, but tends to generate a larger noise.

FIG. 6A is an explanatory view of the suction port 74 of the blower 1x of the comparative example. FIG. 6B is an explanatory view of air flows F1 and F2 in the upper case 71 of the blower 1x of the comparative example. The inner circumferential edge of the suction port 74 has a circular shape when viewed in a direction parallel to the rotation axis A. As illustrated in FIG. 6B, the upper case 71 has a facing surface 715 that faces the shroud 35 of the closed impeller 30 with a predetermined gap therebetween.

As illustrated in FIG. 6B, when the closed impeller 30 rotates, the airflow F1 passes through the closed impeller 30 from the suction port 74 via the opening 352 and flows into the constant width scroll flow passage P. The airflow F2 flows backward between the shroud 35 and the facing surface 715 from the gap between the outer circumferential edge 351 of the shroud 35 and the inner surface of the upper case 71, and flows into the opening 352. Therefore, the airflow F1 and the airflow F2 flowing in different directions collide with each other near the opening 352, and a collision sound is generated. It is considered that such collision between the airflow F1 and the airflow F2 occurs over the entire circumference of the opening 352. Since the opening 352 is close to the suction port 74, the noise due to such collision is large in the blower 1x of the comparative example.

First Embodiment

Next, a blower 1a of a first embodiment will be described. A suction port 74a of the blower 1a in the first embodiment has a shape different from that of the suction port 74 of the blower 1x in the comparative example. The other configurations of the blower 1a and the blower 1x are the same. FIG. 7A is an explanatory view of the suction port 74a of the blower 1a of the first embodiment. FIG. 7B is an explanatory view of air flows F3 and F4 in an upper case 71a of the blower F3 of the first embodiment.

As illustrated in FIG. 7A, the inner circumferential edge of the suction port 74a includes a single arc edge 74a1 and a single straight edge 74a2. The arc edge 74a1 extends in an arc shape about the rotation axis A as viewed in the direction of the rotation axis A. The radius of the arc edge 74a1 is the same as the radius of the suction port 74 in the comparative example. The length of the arc edge 74a1 is longer than the half circumference of the suction port 74 of the comparative example. The straight edge 74a2 is continuous with the arc edge 74a1 and extends linearly when viewed in the direction of the rotation axis A. The straight edge 74a2 is located inside the suction port 74 of the comparative example, but is separated from the rotation axis A. The length of the straight edge 74a2 is shorter than the diameters of the suction port 74 of the comparative example. The arc edge 74a1 and the straight edge 74a2 are smoothly curved and continuous with each other. The area of the suction port 74a is smaller than the area S4 of the suction port 74 of the comparative example, but is larger than the area S6 of the discharge port 76.

As illustrated in FIG. 7B, the airflow F3 passes through the closed impeller 30 via the opening 352 along the straight edge 74a2 of the suction port 74a and flows into the constant width scroll flow path P. The airflow F4 flows backward between the shroud 35 and the facing surface 715 from the gap between the outer circumferential edge 351 of the shroud 35 and the inner surface of the upper case 71, and flows into the opening 352. Here, similarly to the blower 1x of the comparative example, the airflow F3 and the airflow F4 flowing in different directions collide with each other near the opening 352. However, as illustrated in FIG. 6B, the airflow F2 collides with the airflow F1 flowing along the suction port 74 near the opening 352. On the other hand, as illustrated in FIG. 7B, the airflow F4 collides with the airflow F3 flowing along the straight edge 74a2 after flowing between the hub 31 and the shroud 35 through the opening 352. Therefore, when the airflow F4 collides with the airflow F3, the direction of the airflow F4 is substantially along the direction of the airflow F3, and the collision noise is suppressed. Thus, the noise of the blower 1a of the first embodiment is suppressed as compared with the blower 1x of the comparative example.

FIGS. 8A and 8B are views of the blower 1a of the first embodiment in which angular positions of the suction ports 74a are different. A reference line L1 extends from the rotation axis A toward the side where the duct portion 75 protrudes from the scroll portion 73, and is parallel to the duct axis B. An angle line L2 extends radially outward from the rotation axis A and is orthogonal to the straight edge 74a2. In the blower 1a in FIG. 8A, the angle from the reference line L1 to the angle line L2 in the counterclockwise direction is set to 110 degrees. In the blower 1a in FIG. 8B, the above angle is set to 155 degrees. In this way, the angular position of the suction port 74a may be changed according to various conditions.

Second Embodiment

FIG. 9A is an explanatory view of a suction port 74b of a blower 1b of a second embodiment. FIG. 9B is an explanatory view of the airflows F3 and F4 in an upper case 71b of the blower 1b of the second embodiment. As illustrated in FIG. 9A, the inner circumferential edge of the suction port 74b includes two arc edges 74b1 and two straight edges 74b2. The arc edge 74b1 extends in an arc shape about the rotation axis A as viewed in the direction of the rotation axis A. The radius of the arc edge 74b1 is the same as the radius of the suction port 74 of the comparative example. The straight edge 74b2 is continuous with the arc edge 74b1 and extends linearly when viewed in the direction of the rotation axis A. The two arc edges 74b1 are point-symmetrical with respect to the rotation axis A. The two straight edges 74b2 are point-symmetrical with respect to the rotation axis A. Therefore, the suction port 74b is point-symmetrical about the rotation axis A. The area of the suction port 74b is smaller than the area S4 of the suction port 74 in the comparative example and the area of the suction port 74a in the first embodiment, but is larger than the area S6 of the discharge port 76.

As illustrated in FIG. 9B, the airflow F4 collides with the airflow F3 flowing along the straight edge 74b2 of the suction port 74b after flowing between the hub 31 and the shroud 35 through the opening 352. Therefore, when the airflow F4 collides with the airflow F3, the direction of the airflow F4 is substantially along the direction of the airflow F3, and the collision noise is suppressed. Thus, the noise of the blower 1b of the second embodiment is suppressed as compared with the blower 1x of the comparative example.

FIGS. 10A and 10B are views of the blower 1b of the second embodiment in which angular positions of the suction ports 74b are different. The angle line L2 extends radially outward from the rotation axis A and is perpendicular to one of the two straight edges 74b2. The blower 1b in FIG. 10A, the angle is set to 315 degrees. The blower 1b in FIG. 10B, the angle is set to 45 degrees. In this way, the angular position of the suction port 74b may be changed according to various conditions.

Third Embodiment

FIG. 11A is an explanatory view of a suction port 74c of a blower 1c of a third embodiment. FIG. 11B is an explanatory view of the airflows F3 and F4 in an upper case 71c of the blower 1c of the third embodiment. As illustrated in FIG. 11A, the inner circumferential edge of the suction port 74c includes three arc edges 74cl and three straight edges 74c2. The arc edge 74cl extends in an arc shape about the rotation axis A as viewed in the direction of the rotation axis A. The radius of the arc edge 74cl is the same as the radius of the suction port 74 of the comparative example. The straight edge 74c2 is continuous with the arc edge 74cl and extends linearly when viewed in the direction of the rotation axis A. The three arc edges 74cl are point-symmetrical about the rotation axis A. The three straight edges 74c2 are point-symmetrical with respect to the rotation axis A. Therefore, the suction port 74c is point-symmetrical about the rotation axis A. The area of the suction port 74c is smaller than the area S4 of the suction port 74 of the comparative example, the area of the suction port 74a of the first embodiment, and the area of the suction port 74b of the second embodiment, but is larger than the area S6 of the discharge port 76.

As illustrated in FIG. 11B, the airflow F4 collides with the airflow F3 flowing along the straight edge 74c2 of the suction port 74c after flowing between the hub 31 and the shroud 35 through the opening 352. Therefore, when the airflow F4 collides with the airflow F3, the direction of the airflow F4 is substantially along the direction of the airflow F3, and the collision noise is suppressed. Thus, the noise of the blower 1c of the third embodiment is suppressed as compared with the blower 1x of the comparative example.

FIGS. 12A and 12B are views of the blower 1c of the third embodiment in which angular positions of the suction ports 74c are different. The angle line L2 extends radially outward from the rotation axis A and is orthogonal to one of the three straight edges 74c2. In the blower 1c in FIG. 12A, the angle is set to 45 degrees. In the blower 1c in FIG. 12B, the angle is set to 75 degrees. In this way, the angular position of the suction port 74c may be changed according to various conditions.

[Measurement Results]

Next, the measurement results of noise of the blower 1x of the comparative example, the blower 1a of the first embodiment, the blower 1b of the second embodiment, and the blower 1c of the third embodiment will be described. The rotational speed of the closed impeller 30 was kept constant, and the opening degree of a throttle (not illustrated) attached to the discharge port 76 of the duct portion 75 for measurement was changed to change the flow rate of air discharged from the discharge port 76 to 190 L/min, 220 L/min, and 240 L/min, and noise was measured at each flow rate. Further, the noise was measured in the blower having different angles between the reference line L1 and the angle line L2 at the respective flow rates. In the blower 1a of the first embodiment, the noise was measured at the above-described angles of 20 degrees, 65 degrees, 110 degrees, 155 degrees, 200 degrees, 245 degrees, 290 degrees, and 335 degrees. In the blower 1b of the second embodiment, the noise was measured at the above-described angles of 315 degrees, 0 degrees, 45 degrees, and 90 degrees. In the blower 1c of the third embodiment, the noise was measured at the above-described angles of 15 degrees, 45 degrees, 75 degrees, and 105 degrees. Table 1 illustrates the measurement results of noise.

When the flow rate is 190 L/min, the flow rate of the blower 1x of the comparative example was 83.35 dB (A). In the blower 1a of the first embodiment, the noise was reduced more than the noise of the blower 1x of the comparative example in substantially the entire region of the above-described angle. In particular, the reduction in noise was significant at the above-described angles of 20 degrees, 65 degrees, 110 degrees, and 155 degrees.

When the flow rate is 220 L/min, the flow rate of the blower 1x of the comparative example was 88.12 dB (A). In the blower 1a of the first embodiment, the noise was reduced more than the noise of the blower 1x of the comparative example in substantially the entire region of the above-described angle. In particular, the reduction in noise was significant when the above-described angles were 20 degrees, 65 degrees, 110 degrees, 155 degrees, and 335 degrees.

When the flow rate is 245 L/min, the flow rate of the blower 1x of the comparative example was 91.40 dB (A). In the blower 1a of the first embodiment, the noise was reduced more than the noise of the blower 1x of the comparative example in substantially the entire region of the above-described angle.

Therefore, in the blower 1a of the first embodiment, the noise is suppressed regardless of the flow rate by setting the above-described angle within the range of 20 degrees to 155 degrees, and 335 degrees to 20 degrees. In particular, in the blower 1a of the first embodiment, the noise is sufficiently suppressed by setting the above-described angle within the range of 110 degrees to 155 degrees.

In the blower 1b of the second embodiment, the noise was reduced more than that of the blower 1x of the comparative example in substantially the entire region of the angle described above in any case of the flow rate. In particular, in the blower 1b of the second embodiment, the noise is sufficiently suppressed by setting the above-described angle within the range of 315 degrees to 45 degrees.

In the blower 1c of the third embodiment, the noise was reduced more than that of the blower 1x of the comparative example in substantially the entire region of the angle described above in any case of the flow rate. In particular, in the blower 1c of the third embodiment, the noise is sufficiently suppressed by setting the above-described angle within the range of 45 degrees to 75 degrees.

While the exemplary embodiments of the present disclosure have been illustrated in detail, the present disclosure is not limited to the above-mentioned embodiments, and other embodiments, variations and variations may be made without departing from the scope of the present disclosure.